DESCRIPTION

[Technical field]

The object of the present invention is a household appliance for drying laundry.

[State of the art]

A drier with a heat pump equipped with a condenser and an evaporator is known.

This type of drier comprises a drying compartment in which a rotating drum is located and the drying air is taken from the compartment and treated by the heat pump prior to being re-introduced therein.

In particular, the evaporator of the heat pump allows for condensation of the moisture present in the air taken from the washing compartment (this is accompanied by the evaporation of a working fluid that circulates in the heat pump) . The condenser of the heat pump brings about the heating of the air extracted from the compartment and previously dehumidified (this is accompanied by the condensation of the working fluid that circulates in the heat pump) .

At this point, the air extracted from the drying compartment can be re-directed back towards the laundry items to be dried.

The working fluid circulating in the heat pump downstream of the evaporator and upstream of the condenser undergoes an increase in pressure in a compressor.

The use of a variable speed compressor is known for the best adaptation of the operation of the heat pump to various operating modes. A compressor such as this makes it possible for example to increase the rotation speed so as to reduce the initial transient. Likewise, the compressor makes it possible to reduce the rotation speed in a final step of the drying cycle or when operating the drier with a small load of laundry in the drum (thus allowing for lower energy consumption on the part of the compressor) .

One drawback of this design solution relates to the fact that the cost of a variable speed compressor is considerable and this affects the costs of the entire household appliance.

[Aim of the invention]

In this context, the technical task underlying the present invention is to overcome the above-mentioned drawbacks and to make available a household appliance that makes it possible to optimize the operation of the drying cycle.

The defined technical task and the specified aims are substantially achieved by a household appliance that comprises the technical characteristics set forth in one or more of the appended claims.

[Brief description of the drawings]

Further characteristics and advantages of the present invention will become more apparent from the approximate and thus non-limiting description of a preferred, but not exclusive, embodiment of a household appliance for drying laundry, as illustrated in the accompanying drawings, in which Figure 1 shows a schematic view of a household appliance according to the present invention. In the accompanying figures, a household appliance for drying laundry is indicated by the reference number 1. This household appliance 1 can be a washer-drier or a drier, for example.

The household appliance 1 comprises:

-a rotating drum 2 designed to house the laundry to be dried;

-a drying compartment 20, in which the drum 2 is located;

-a line 3 for taking drying air from said compartment 20 and for re-introducing the same air in the compartment 20;

-a heat pump 4 for treating the drying air, in said heat pump 4 circulating a working fluid.

[Detailed description of preferred embodiments of the invention]

The heat pump 4 comprises a circuit 40 in which the working fluid circulates. This circuit 40, in turn, comprises a condenser 44 for condensing the working fluid, said condenser 44 interacting with the drying air flowing in said line 3.

The circuit 40 comprises a first and a second evaporator 41, 42 for evaporating the working fluid in thermal contact with the drying air flowing in said line 3; following the direction of flow of the drying air along said line 3, the condenser 44 is downstream of the first and the second evaporator 41, 42. The first and/or the second evaporator 41, 42 determine (s) the condensation of the moisture present in the drying air. The condenser 44 allows for heating the drying air previously dehumidified by the first and/or second evaporator 41, 42. This heating process takes place prior to the re-introduction of the heating air in the compartment 20. A movement means 6 for moving the drying air along the line 3 is conveniently located along the line 3.

The circuit 40 further comprises a working fluid conduit 43 that comprises a zone 430 in which it divides into a first and a second branch 431, 432 comprising a first and a second thermal expansion member 61, 62, respectively. The first branch 431 passes through said first evaporator 41 and the second branch 432 passes through said second evaporator 42. The zone 430 in which the conduit 43 divides is downstream of the condenser 44 and upstream of the first and the second evaporator 41, 42 according to the direction of flow of the working fluid. The first and the second evaporator 41, 42 are arranged in parallel. The circuit 40 further comprises a compressor 46 for compressing the working fluid. The compressor 46 is located downstream of the first and the second evaporator 41, 42 and upstream of the condenser 44 along the direction of flow of the working fluid.

Conveniently, the compressor 46 is a fixed speed compressor .

The circuit 40 further comprises control means 45 for controlling the supply of working fluid coming from the first and the second branch 431, 432 in said compressor 46.

The control means 45 comprises a valve 451 in which the first and the second branch 431, 432 merge. The valve 451 is located in a zone 433 that reconnects the first and the second branch 431, 432. This valve 451 can conveniently take on at least one configuration in which it enables the passage of the working fluid coming only from the first branch 431.

The valve 451 can take on a configuration in which it enables the passage of the working fluid coming only from the second branch 432.

The valve 451 can take on a configuration in which it enables the passage of the working fluid coming from both the first branch and the second branch 431,432.

The valve 451 can conveniently take on a configuration in which it prevents the passage of the working fluid from both the first and the second branch 431, 432.

This valve 451 conveniently comprises a casing. The casing is conveniently provided with openings for connection with the first branch 431, the second branch 432 and the compressor 46. A shutter provided with at least one through cavity is present in the casing. Depending on the orientation of the shutter within the casing, this cavity sets the zones upstream and downstream of the valve 451 in fluid communication. 451. This cavity can also have branches, for example for setting a number of input zones upstream of the valve 451 in fluid communication with a single output zone downstream of the valve 451.

In the preferred solution, the valve 451 is a three-way ball valve.

The first and the second thermal expansion members 61, 62 are capillaries that define a reduction of the section for passage of the first and the second branch 431, 432. The first and/or the second thermal expansion member 61, 62 define (s) a reduction of the passage section. The first thermal expansion member 61 is in series with the first evaporator 41, and the second thermal expansion member 62 is in series with the second evaporator 42.

The first thermal expansion member 61 has different geometric characteristics with respect to said second thermal expansion member 62. In this manner, a different head loss is obtained.

The first evaporator 41 and the second evaporator 42 have different heat exchange capacities. This allows for even more versatile operation of the household appliance 1.

In fact, the control means 45 comprises an electronic control unit that automatically commands the valve 451 based on pre-established parameters.

In this regard, an object of the present invention is also a method of operation of a household appliance 1 having one or more of the characteristics indicated hereinabove. The method conveniently comprises the steps of:

-determining a value of the weight of the laundry to be dried that has been placed in the drum 2 (for example by measuring the increase in the weight of the drum or by means of specific algorithms for estimating the load inserted in the drier) ;

-having said working fluid flow in both the first and the second evaporator 41, 42 should said value (of the weight of the laundry) exceed a pre-established threshold. The method further comprises having said fluid flow only in the first or in the second evaporator 41, 42 should said value (of the weight of the laundry) fall short of the pre-established threshold. The command for having the working fluid flow in both the first and the second evaporator 41, 42, or only in the first or the second evaporator 41, 42, is given by said electronic unit based on pre-established parameters.

In an alternative, not preferred solution, the steps described above are slightly modified as follows: if the value of the weight of the laundry (either measured or estimated by means of algorithms) exceeds said threshold, the working fluid will be allowed to flow only in the first evaporator 41; if the value falls short of the threshold, the working fluid will be allowed to flow only in the second evaporator 42. Passage into the first evaporator 41 corresponds to passage in the first branch 431 and passage into the second evaporator 42 corresponds to passage in the second branch 432.

An object of the present invention is a method of operation of the household appliance 1 that comprises the step of having the fluid flow only in the first evaporator 41 in the case in which a user selects a command that signals the presence of a small load in the drum 2 to the household appliance 1.

As regards the considerations stated above, they are justified by the fact that if the household appliance 1 is operating with a full load, a greater amount of working fluid will be needed for the purpose of enabling more dehumidification of the drying air (and therefore the working fluid needs to flow in both the first and the second evaporator 41, 42) . If instead the household appliance 1 is operating with smaller load, a lower flow rate of the working fluid may be necessary, given that dehumidification is ensured in any case (and operation with a reduced flow rate is advantageous given that it requires lower energy consumption levels on the part of the compressor 46) .

An object of the present invention is also a method of operation of a household appliance comprising the steps of:

-having said working fluid flow in both the first and the second evaporator 41,42 in a first step upon start ^¬ up of a drying cycle;

-having said working fluid flow only in the first evaporator 41 in a second step following the first step .

In fact, upon start-up of the household appliance 1, the drying air is at ambient temperature and the maximum flow rate of the working fluid may be necessary to facilitate the process of heating the same air in the condenser 44.

When running, however, the incoming drying air in the line 3 is already at a higher temperature and the moisture level thereof is also lower. Under these conditions, a more limited heat exchange may be sufficient, thus enabling a reduction of the power absorbed by the compressor 46.

The invention makes it possible to achieve multiple advantages. First of all, it makes it possible to modulate dehumidification capacity, without the use of a variable speed compressor. In fact, a variable speed compressor entails high costs, for installation and for maintenance. The present invention thus makes it possible to regulate the cooling capacity of the heat pump based on the load and/or the program selected. Furthermore, the positioning of the valve 451 downstream of the first and second thermal expansion member 61, 62 makes it possible to position the valve 451 in a low-pressure zone; as a result, the seals and geometry of the valve 451 will be such as to resist lower pressures (and therefore this component entails lower costs) . Moreover, in this manner, the valve 451 offers a greater degree of reliability.

The invention thus conceived is susceptible to numerous modifications and variants, all of which falling within the scope of the inventive concept characterizing the invention. Moreover, all details may be replaced with other technically equivalent elements. All the materials used, as well as the dimensions, may in practice be of any type, according to needs.